OBJECTIVES: Studies suggest a genetic influence on levels of interleukin-1beta (IL-1beta) in gingival crevicular fluid (GCF). Levels of IL-1beta in GCF, however, are also dependent upon the clinical parameters at the site of collection, including probing depth (PD) and level of attachment (AL). To examine this issue, IL-1beta in GCF was evaluated from patients with varying degrees of periodontal disease. The influence of both the status of the patient and the probing depth at the sampled sites were considered in the analysis. MATERIAL AND METHODS: GCF IL-1beta was determined by ELISA at 6-8 molar sites from 29 non-smoking adults with mild, moderate, or severe periodontal disease at baseline, 2 weeks, and 24 weeks following scaling and root planing. For later analysis, patients were dichotomized on the basis of disease severity (mild/moderate vs severe). Sampled sites were classified at baseline by PD as, shallow (<4 mm), intermediate (4-6 mm), or deep (>6 mm). RESULTS: PD and AL were each strongly correlated with IL-1beta levels at baseline. However, patients with severe disease had higher levels of IL-1beta in each PD category than those with mild/moderate disease. As compared to patients with mild/moderate disease, IL-1beta levels in shallow sites from patients with severe disease was elevated nearly 2 fold (p<0.001). IL-1beta levels were reduced in all groups at 2 weeks and were still significantly reduced in patients with mild/moderate disease at 24 weeks. At 24 weeks IL-1beta returned to near baseline levels in patients with severe disease. CONCLUSION: While PD and AL are each associated with increased GCF IL-1beta, patients with severe disease show higher IL-1beta GCF levels in shallow sites, suggesting that high GCF IL-1beta expression is in part a host trait, and not strictly a function of clinical parameters.